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1. Field of the Invention
The invention relates to bar code reading and in particular to a new symbol with structure and features that make it particularly suitable for consumer-scanning applications. Its features include a compact start pattern that can be found without compute-intensive ratio checks, and an overall structure that supports variable-length messages while providing strong protection against short reads.
2. Background of the Invention
Bar code symbols are formed from bars or elements typically rectangular in shape with a variety of possible widths. The specific arrangement of elements defines the character represented according to a set of rules and definitions specified by the code or xe2x80x9csymbologyxe2x80x9d used. The relative size of the bars and spaces is determined by the type of coding used as is the actual size of the bars and spaces. The number of characters (represented by the bar code symbol) is referred to as the density of the symbol. To encode the desired sequence of the characters, a collection of element arrangements are concatenated together to form the complete bar code symbol, with each character of the message being represented by its own corresponding group of elements. In some symbologies, a unique xe2x80x9cstartxe2x80x9d and xe2x80x9cstopxe2x80x9d character is used to indicate when the bar code begins and ends. A number of different bar code symbologies are in widespread use including UPC/EAN, Code 39, Code 128, Codeabar, and Interleaved 2 of 5.
In order to increase the amount of data that can be represented or stored on a given amount of surface area, several more compact bar code symbologies have been developed. One of these code standards, Code 49, exemplifies a xe2x80x9ctwo dimensionalxe2x80x9d symbol by reducing the vertical height of a one-dimensional symbol, and then stacking distinct rows of such one dimensional symbols, so that information is encoded both vertically as well as horizontally. That is, in Code 49, there are several rows of bar and space patterns, instead of only one row as in a xe2x80x9cone dimensionalxe2x80x9d symbol. The structure of Code 49 is described in U.S. Pat. No. 4,794,239. Another two-dimensional symbology, known as xe2x80x9cPDF417xe2x80x9d, is described in U.S. Pat. No. 5,304,786.
Still other symbologies have been developed in which the symbol is comprised not of stacked rows, but a matrix array made up of hexagonal, square, polygonal and/or other geometric shapes, lines, or dots. Such symbols are described in, for example, U.S. Pat. Nos. 5,2276,315 and 4,794,239. Such matrix code symbologies may include Vericode, Datacode, and MAXICODE.
Ever since the advent of the Universal Product Code in the 1970""s, linear bar code symbols have been widely adopted as an inexpensive but effective way of automating the link between printed numbers on paper and computer databases. Each xe2x80x9csymbologyxe2x80x9d has its own advantages for certain applications. Because bar codes are so common in our daily environment, and used in so many different applications, it is often important that a symbology, or a distinct variant of a symbology, be dedicated to one specific application. For example, a bar code scanning system may read a barcode encoding a string of digits such as xe2x80x9c12345678905xe2x80x9d. It is very important that the system can unequivocally determine that this string is to be used to look up the price of a grocery item, and that the price can be found, using the decoded string of digits as a key, in a database of numbers assigned by the Uniform Code Council for this purpose. In the past many other symbologies and symbology variants have also been reserved for such specific uses, such as a Code 128 symbol for marking medical instruments, a 14-digit Interleaved Two-of-Five symbol for marking cases for logistics tracking, and a 6-digit Code 39 symbol for marking Telecommunications equipment.
One aspect held in common by all of the above traditional barcode applications, is that a worker (such as a checkout clerk at a supermarket) will be trained and paid to scan the specific kind of barcode required by the application. Recently, however, as the cost of computers, and of scanning hardware, has decreased, a new set of consumer-scanning applications have become feasible.
Consumer-scanning applications will in principle have many requirements in common with traditional bar code applications, except that the consumer-scanning application will increase the difficulty of meeting some of these requirements. In addition, consumer scanning places at least one new requirement on the symbology. The following paragraphs discuss the new requirements, and then the other requirements that differ in degree.
By definition, the consumer scanning system will be used by untrained and unpaid operators. An unpaid operator will simple abandon consumer scanning if it is perceived as difficult or unreliable. An untrained operator will put the scanning system at a disadvantage through poor technique (such as scanning at an angle, or scanning too close to completely cover the bar code). Thus, the ideal consumer-scanning symbology will facilitate easy intuitive scanning, and will survive an untrained operator""s mistakes without these turning into decode errors (such as short reads) that could get into the system.
Traditional linear bar code symbologies are xe2x80x9cframedxe2x80x9d by relatively large areas, to the left and to the right of the bar code, that must be kept clear of all printing. These areas, called xe2x80x9cQuiet Zonesxe2x80x9d, provide technical benefits that make designing and scanning such symbologies easier. However, these Quiet Zones require additional space to be reserved for the barcode. Moreover, they prevent graphics or text from being tightly coupled to the barcode. This is a problem in the consumer scanning environment, where graphical and textual clues, placed immediately adjacent to the bar code, can help untrained consumer operators find the bar code within graphics, and help them understand what the result of scanning a given consumer barcode will be. Thus, the ideal consumer scanning symbology will allow text and graphics to be tightly coupled to the bar code, not kept distant from it.
Many traditional bar code applications need to fit the printed symbols in a relatively small area. Consumer scanning applications increase the importance of this requirement, as the bar codes will need to fit in constrained spaces such as to mark line items in catalogue tables, and to fit within a single line of text in a newspaper article. Thus, the ideal consumer scanning symbology needs to minimize both the height and the length of the printed bar code.
Many traditional bar code applications are cost-sensitive. However, consumer-scanning applications are extremely cost-sensitive. Thus, the ideal consumer scanning symbology can be scanned by a broad range of low-cost scanning technologies, and will be decodable by a low-cost, low-capability microprocessor system.
Most traditional bar code applications suffer from some variation in print quality, often resulting from attempts to save operating costs of label stock and regular printer maintenance. However, extremely poor print quality is usually avoided in business scanning situations, because of the need to maintain a good business relationship between the organization that prints the barcodes, and the organization that must scan them. Consumer-scanning applications are more likely to experience severe print quality problems for two reasons. First, the checks and balances between a supplier and a receiver in a business relationship will not be present in a consumer-scanning application. Second, consumer barcodes will be printed, not on labels, but on newspapers, in yellow pages, and on other forms of paper that are not amenable to high-accuracy printing. Thus, the ideal consumer scanning symbology can tolerate severe printing defects without an increased risk of false reads (mis-decodes).
Unlike with traditional bar code applications, consumer-scanning printing will often be done without benefit of professional expertise. A particular concern is that the traditional white-space requirements to the left and right of the barcode would often be ignored, in an attempt to fit the barcode into the requirements of a classified advertisement or other space-constrained application. Thus, the ideal consumer scanning symbology would be tolerant of text and graphics immediately adjacent to the bar code.
1. Objects of the Invention
It is a general object of the present invention to provide an improved bar code symbology.
It is another object of the invention to provide a bar code reader capable of reading the improved symbology.
It is a further object of the present invention to provide a printer for printing the improved symbology.
It is a still further object of the present invention to provide software capable of decoding the improved symbology.
It is an even further object of the invention to provide a method which can be used to accomplish one or more of the above objectives.
Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detail description, as well as by practice of the invention. While the invention is described below with reference to preferred embodiments, it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional applications, modifications and embodiments in other fields, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of significant utility.
It is an object of the present invention to provide a machine-readable symbology, in which consumer-friendly text and graphics may be printed in direct contact with the leftmost and rightmost bars of the symbol, and may even coincide with these leftmost and rightmost bars.
It is still another object of the present invention to provide a variable-length linear symbology that does not require large white spaces at either end of the bar code, and yet resists short-reads without needing to explicitly encode the length of the symbol.
It is an object of the present invention to provide a machine-readable symbology that includes a space-efficient xe2x80x9cfinderxe2x80x9d pattern, that facilitates a rapid search through text and graphics without the need to perform arithmetic upon sums of multiple bars and spaces.
It is a goal of the present invention to provide a machine-readable symbology that includes space-efficient xe2x80x9cStartxe2x80x9d and xe2x80x9cStopxe2x80x9d patterns, that are also unique patterns that cannot be found at any incorrect location within the bar code symbol, even if the symbol contains print defects, or has been scanned at an angle, or at the wrong distance (resulting in an out-of-focus or otherwise distorted signal).
2. Summary of the Invention
The present invention provides a bar code symbology derived from a set of patterns of bar and spaces in which each character spans a distance of m module widths and is represented by n bars and p spaces; and the largest single bar or space is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein the improvement consists of the exclusion from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.
The present invention further provides a information bearing machine-readable carrier including a substrate; and a pattern of bars and spaces on said substrate in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein excluded from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.
The present invention further provides an imager for obtaining image data of a target in an image field the target including a symbol having a pattern of bars and spaces in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein excluded from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol; and a decoder for processing the image data to derive the information contained in the symbol.
The novel features and characteristics of the invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof, will be vest understood by reference to a detailed description of a specific embodiment, when read in conjunction with the accompanying drawings.